Common name and meaning
The common name is the Polar Bear. It was named for the fact that it lives in the arctic.
MIGRATION: Some polar bears make extensive north-south migrations in response to ice packs receding northward in the spring and advancing southward in the fall. In addition, individuals may travel vast distances to find mates or food and have been seen 100 miles from the nearest land- or icefall. In October and November, males head out onto the pack ice where they spend the winter, while pregnant females seek sites on land or nearshore sea ice to dig dens in the snow, where they spend the winter and give birth.
EVOLUTION: It appears that when large frozen expanses of ice with seals on them appeared, the land bears were able to go out and scavenge on dead ones or stalk live ones.
We see the same sort of thing today with the brown (grizzly) bears along the northern coast of western Canada and Alaska that are seen out on the ice in early spring scavenging on seals killed by bears and apparently going hunting on their own as well. There is a great deal of variation in coat color of grizzlies, so I expect the lighter-colored ones probably were more successful so that natural selection favored them and, over the longer term, they simply became white.
The same sort of selection for white color appears to have taken place with Arctic wolves.
DNA evidence found by Icelandic geologist Ólafur Ingólfsson suggests that polar bears were just beginning to spread out across their Arctic habitat between the last two ice ages, when Earth's climate was warmer than it is today. In just 1000 generations or so, U. maritimus morphed from a stocky brown bear to a long-necked bear with thick fatty layers and the signature white coat. The Svalbard area, north of the Arctic Circle and far from the competitors inhabiting the continental land masses, offered just the right refuge where the bears could persist through the warming period before the last ice age and then begin to adapt to a life amid the frozen sea.
Berardelli, Phil. "Early Polar Bear Discovered in Arctic Tundra." - ScienceNOW. Science Magazine, 1 Mar. 2010. Web. 20 Apr. 2013. <http://news.sciencemag.org/sciencenow/2010/03/early-polar-bear-discovered-in-a.html>.
EVOLUTION: It appears that when large frozen expanses of ice with seals on them appeared, the land bears were able to go out and scavenge on dead ones or stalk live ones.
We see the same sort of thing today with the brown (grizzly) bears along the northern coast of western Canada and Alaska that are seen out on the ice in early spring scavenging on seals killed by bears and apparently going hunting on their own as well. There is a great deal of variation in coat color of grizzlies, so I expect the lighter-colored ones probably were more successful so that natural selection favored them and, over the longer term, they simply became white.
The same sort of selection for white color appears to have taken place with Arctic wolves.
DNA evidence found by Icelandic geologist Ólafur Ingólfsson suggests that polar bears were just beginning to spread out across their Arctic habitat between the last two ice ages, when Earth's climate was warmer than it is today. In just 1000 generations or so, U. maritimus morphed from a stocky brown bear to a long-necked bear with thick fatty layers and the signature white coat. The Svalbard area, north of the Arctic Circle and far from the competitors inhabiting the continental land masses, offered just the right refuge where the bears could persist through the warming period before the last ice age and then begin to adapt to a life amid the frozen sea.
Berardelli, Phil. "Early Polar Bear Discovered in Arctic Tundra." - ScienceNOW. Science Magazine, 1 Mar. 2010. Web. 20 Apr. 2013. <http://news.sciencemag.org/sciencenow/2010/03/early-polar-bear-discovered-in-a.html>.